Producing method for gold sputtering target and producing method for gold film

ABSTRACT

A production method for a gold sputtering target includes: producing a gold sputtering target which is made of gold and inevitable impurities and in which an average value of Vickers hardness is 40 or more and 60 or less, an average value of crystal grain size is 15 μm or more and 200 μm or less, and the {110} plane of gold is preferentially oriented to a surface to be sputtered of the gold sputtering target.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of prior International ApplicationNo. PCT/JP2018/044717, filed on Dec. 5, 2018 which is based upon andclaims the benefit of priority from Japanese Patent Applications No.2017-234730 filed on Dec. 6, 2017; the entire contents of all of whichare incorporated herein by reference.

FIELD

The present invention relates to a producing method for a goldsputtering target and a producing method for a gold film.

BACKGROUND

An Au film formed using a gold (Au) sputtering target has excellentchemical stability and electrical characteristics of Au itself and hasthus been used in various fields. For example, a quartz oscillatordevice uses an Au sputtered film as, e.g., an excitation electrode to beformed on both surfaces of a quartz chip. In such a quartz oscillatordevice, an oscillation frequency is adjusted by the thickness of the Aufilm and, thus, there is demanded an Au sputtering target allowing an Aufilm having a uniform thickness distribution to be formed duringsputtering.

A sputtering target typically has a circular or rectangular plate shape,which is used for planar magnetron sputtering. In addition, acylindrical sputtering target is also known. The cylindrical sputteringtarget is higher in terms of the usage rate of a target material duringsputtering than the plate-shaped sputtering target, so that the use ofsuch a cylindrical sputtering target has begun for ceramics materialsand then for metal- and alloy-based targets. Further, the use of thecylindrical sputtering target for noble metal targets such as a silver(Ag) target is being studied (see Patent Documents 1 and 2).

The use of the cylindrical target, as well as the plate-shapedsputtering target, is being studied also for the Au sputtering targetfor Au film formation. However, it is difficult for conventional Ausputtering targets to achieve high film thickness distributionuniformity required for the Au film used as an electrode of, forexample, a quartz oscillator device, irrespective of whether they are ofa plate-shaped or cylindrical type. In particular, the cylindrical Ausputtering target has a great difficulty in improving the Au filmthickness distribution uniformity in terms of processing accuracy forthe cylindrical shape.

The following describes in more detail the quartz oscillator devices.The quartz oscillator devices are used for mobile devices, for example,and are required to be small in size, lightweight, and thin inassociation with a demand for reduction in size, weight, and thicknessof the mobile devices. For example, the package size of the quartzoscillator device has been reduced from 5.0 mm×3.2 mm (5032 size) to 3.2mm×2.5 mm (3225 size), 2.5 mm×2.0 mm (2520 size), 2.0 mm×1.6 mm (2016size), and 1.6 mm×1.2 mm (1612 size) and, correspondingly, a quartzoscillator (quartz chip) itself is being miniaturized.

The quartz oscillator device has the Au film on both surfaces of aquartz chip (blank) as an electrode, as described above. The quartz chiphas an outer shape with rounded corners which can be obtained by etchingor by mechanical treatment after press punching, so as to bring thecenter of gravity close to the center for frequency stabilization. Whenthe quartz chip has a rough surface, the frequency characteristicsthereof is deteriorated, so that the quartz chip is required to have asurface with high smoothness. Similarly, an electrode to be formed inthe quartz chip is required to have high smoothness, i.e., to be smallin film thickness variation. The electrode has a three-dimensionalstructure having a given thickness, so that, in a miniaturized quartzchip, the film thickness variation has a greater influence on thethree-dimensional structure. Thus, in order to respond to theminiaturization of the quartz oscillator device and the like, the filmthickness variation of the Au film used as the electrode is required tobe smaller.

In a 32 kHz quartz oscillator for a timepiece, a variation in the massof the Au film has a great influence on the frequency characteristics.The 32 kHz quartz oscillator includes a fork type and a tuning fork typein terms of shape. The tuning fork type quartz oscillator is suitablefor miniaturization; however, the mass variation of the Au film affectsthe frequency characteristics, so that a reduction in the mass variationderived from the Au film thickness variation is strongly required. Thetuning fork type quartz oscillator has a difficulty in frequencyadjustment, and thus various modifications have been made to cope withthe drawback. For example, as for the formation method of the Au film,sputtering is now replacing vapor deposition. Further, a part of the Aufilm formed by sputtering is removed by laser beam for mass adjustment,or a weight for mass adjustment is formed during formation of the Aufilm by sputtering. In such a situation, when the mass variation derivedfrom the Au film thickness variation can be reduced, the time andtrouble required for frequency adjustment can be significantly reduced.In particular, the influence of the film thickness variation becomesgreater as the quartz oscillator is reduced in size, with the resultthat the mass is more likely to vary. Also in this respect, the filmthickness variation of the Au sputtered film is required to be reduced.

SUMMARY

The object of the present invention is to provide a gold sputteringtarget production method allowing improvement in uniformity of the filmthickness distribution of a gold film and a gold film production methodcapable of improving uniformity in film thickness distribution.

A production method for a gold sputtering target according to thepresent invention includes: producing a gold sputtering target which ismade of gold and inevitable impurities and in which an average value ofVickers hardness is 40 or more and 60 or less, an average value ofcrystal grain size is 15 μm or more and 200 μm or less, and the {110}plane of gold is preferentially oriented to a surface to be sputtered ofthe gold sputtering target.

A production method for a gold film according to the present inventionincludes: preparing a gold sputtering target which is made of gold andinevitable impurities and in which an average value of Vickers hardnessis 40 or more and 60 or less, an average value of crystal grain size is15 μm or more and 200 μm or less, and a {110} plane of gold ispreferentially oriented to a surface to be sputtered of the goldsputtering target; and forming a gold film on a film-forming basematerial through sputtering of the gold sputtering target.

EFFECT

According to the gold sputtering target production method of the presentinvention, it is possible to produce with good reproducibility a goldsputtering target allowing a gold film excellent in uniformity of a filmthickness distribution to be obtained. This can improve uniformity ofthe film thickness distribution of the gold film with goodreproducibility. Further, according to the gold film production methodof the invention, it is possible to provide a gold film excellent inuniformity of the film thickness distribution with good reproducibility.

DETAILED DESCRIPTION

Hereinafter, an embodiment for practicing the present invention will bedescribed. A sputtering target produced by a production method accordingto the embodiment is made of gold (Au) and inevitable impurities. Theinevitable impurities (elements other than Au) contained in the Ausputtering target are not limited to particular elements. The purity ofAu in the sputtering target is determined according to the applicationof the target or application of a film formed using the target and isset to, for example, 99.99% or more. The use of the sputtering targethaving an Au purity of 99.99% allows a high-purity Au film to beobtained. Further, the upper limit of the Au purity in the sputteringtarget is not limited to a particular value and is typically less than99.999% considering, for example, the production process and productioncost of the Au sputtering target and hardness of the Au sputteringtarget and practically preferably 99.990% or more and 99.998% or less.

The shape of the Au sputtering target according to the embodiment is notlimited to a particular shape and may be a plate shape or a cylindricalshape. The plate-shaped sputtering target typically includes, forexample, a polygonal (e.g., circular or rectangular) plate-shapedsputtering target. Such a polygonal plate-shaped sputtering target mayhave any structure; for example, it may have a hollow portion formed byremoving a part of the circular plate or polygonal plate or may have aslope, a convex portion, or a concave portion in a part of the surfaceof the circular plate or polygonal plate. Similarly, the cylindricalsputtering target is not limited to a particular dimension, and thedimension thereof is selected according to a sputtering apparatus. Atypical cylindrical sputtering target has an outer diameter of 50 mm ormore and 170 mm or less, an inner diameter of 20 mm or more and 140 mmor less, and a length of 100 mm or more and 3000 mm or less, for exampleSuch an Au sputtering target has a surface to be sputtered (sputteringsurface). The plate surface serves as the sputtering surface in theplate-shaped sputtering target, and the surface of the cylinder(cylindrical surface) serves as the sputtering surface in thecylindrical sputtering target.

The Au sputtering target according to the embodiment preferably has aVickers hardness of 40 or more and 60 or less. When an Au splutteringtarget having the above Vickers hardness is used to perform sputtering,an Au film excellent in uniformity of a thickness distribution can beformed. That is, the fact that the Vickers hardness of the Au sputteringtarget is more than 60 HV means that strain generated during productionremains in the Au sputtering target. In such a case, particles ejectedfrom the target fly non-uniformly during sputtering, deterioratinguniformity of the film thickness distribution. The Vickers hardness ofthe Au sputtering target is more preferably 55 HV or less. Further,application of heat during sputtering changes hardness or crystal grainsize, which also deteriorates uniformity of the particle flyingproperty. On the other hand, when the Vickers hardness of the Ausputtering target is less than 40 HV, crystal orientation may collapsein association with occurrence of crystal grain growth, whichdeteriorates uniformity of the film thickness distribution. The Vickershardness of the Au sputtering target is preferably 45 HV or more.

The Vickers hardness of the Au sputtering target is measured as follows.In the case of the plate-shaped sputtering target, the following ninemeasurement points are set: three points set at 10 mm intervals on astraight line in a surface to be sputtered (sputtering surface), threepoints selected respectively from three segmented areas obtained bydividing, into three, a first cross section perpendicular to thesputtering surface in the thickness direction (in the followingExamples, three points set at 1.5 mm intervals on a straight lineextending in the thickness direction of a sample having a 5 mmthickness), and three points selected respectively from three areasobtained by dividing, into three, a second cross section perpendicularto the sputtering surface and the first cross section in the thicknessdirection (in the following Examples, three points set at 1.5 mmintervals on a straight line extending in the thickness direction of asample having a 5 mm thickness). Then, the Vickers hardness is measuredat the above nine measurement points with a 200 gf test force (pressingload). An average value (HV_(av1)) of the Vickers hardness in thesputtering surface, an average value (HV_(av2)) of the Vickers hardnessin the first cross section, and an average value (HV_(av3)) of theVickers hardness in the second cross section are determined. The averagevalues (HV_(av1)/HV_(av2), and HV_(av3)) in the sputtering surface,first cross section, and second cross section are further averaged, andthe obtained average value is defined as an average value (HV_(tav)) ofthe Vickers hardness of the entire plate-shaped Au sputtering target.

In the plate-shaped Au sputtering target, the ratio (HV_(av1)/HV_(tav))of the average value (HV_(av1)) of the Vickers hardness in thesputtering surface to the Vickers hardness (HV_(tav)) of the entiretarget, the ratio (HV_(av2)/HV_(tav)) of the average value (HV_(av2)) ofthe Vickers hardness in the first cross section to the Vickers hardness(HV_(tav)) of the entire target, and the ratio (HV_(av3)/HV_(tav)) ofthe average value (HV_(av3)) of the Vickers hardness in the second crosssection to the Vickers hardness (HV_(tav)) of the entire target eachpreferably fall within the range of 0.8 to 1.2. That is, a variation inthe Vickers hardness of the Au sputtering target is preferably within±20%. By thus reducing the location-dependent variation in the Vickershardness of the Au sputtering target, the flying direction of particlesduring sputtering is made uniform, which improves the uniformity of thefilm thickness distribution.

In the case of the cylindrical Au sputtering target, the following ninemeasurement points are set: three points set at 10 mm intervals on afirst straight line extending parallel to the cylindrical axis in thesputtering surface (cylindrical surface), three points set at 10 mmintervals on a second straight line obtained by rotating the firststraight line by 90°, and three points selected respectively from threeareas obtained by dividing, into three, a cross section perpendicular tothe cylindrical axis in the thickness direction (in the followingExamples, three points set at 1.5 mm intervals on a straight lineextending in the thickness direction of a sample having a 5 mmthickness). Then, the Vickers hardness is measured at the above ninemeasurement points with a 200 gf test force (pressing load). An averagevalue (HV_(av1)) of the Vickers hardness on the first straight line inthe sputtering surface, an average value (HV_(av2)) of the Vickershardness on the second straight line, and an average value (HV_(av3)) ofthe Vickers hardness in the cross section are determined. The averagevalues (HV_(av1), HV_(av2), and HV_(av3)) of the sputtering surface andcross section are further averaged, and the obtained average value isdefined as an average value (HV_(tav)) of the Vickers hardness of theentire cylindrical Au sputtering target.

In the cylindrical Au sputtering target, the ratio (HV_(av1)/HV_(tav))of the average value (HV_(av1)) of a first Vickers hardness in thesputtering surface to the Vickers hardness (HV_(tav)) of the entiretarget, the ratio (HV_(av2)/HV_(tav)) of the average value (HV_(av2)) ofa second Vickers hardness in the sputtering surface to the Vickershardness (HV_(tav)) of the entire target, and the ratio(HV_(av3)/HV_(tav)) of the average value (HV_(av3)) of the Vickershardness in the cross section to the Vickers hardness (HV_(tav)) of theentire target each preferably fall within the range of 0.8 to 1.2. Thatis, a variation in the Vickers hardness of the Au sputtering target ispreferably within ±20%. By reducing the location-dependent variation inthe Vickers hardness of the cylindrical Au sputtering target, the flyingdirection of particles during sputtering is made uniform, which improvesthe uniformity of the film thickness distribution. The cylindrical Ausputtering target is rotated during sputtering, whereby the entirecylindrical surface is sputtered, so that the reduction in thelocation-dependent variation in the Vickers hardness of the sputteringsurface (cylindrical surface) can improve the uniformity of the filmthickness distribution.

The Au sputtering target according to the embodiment preferably has anaverage crystal grain size of 15 μm or more and 200 μm or less. Byperforming sputtering using the Au sputtering target having such anaverage crystal grain size, the film thickness distribution of the Aufilm can be further improved. When the average crystal grain size of theAu sputtering target is less than 15 μm, particles ejected from thetarget fly non-uniformly during sputtering, which may deteriorateuniformity of the film thickness distribution. The average crystal grainsize of the Au sputtering target is more preferably 30 μm or more. Whenthe average crystal grain size of the Au sputtering target exceeds 200μm, flying property of particles during sputtering lowers, which maydeteriorate uniformity of the film thickness distribution. The averagecrystal grain size of the Au sputtering target is more preferably 150 μmor less.

The average crystal grain size of the Au sputtering target is measuredas follows. In the case of the plate-shaped Au sputtering target, thefollowing nine measurement points are set: three points set at 10 mmintervals on a straight line in the sputtering surface, three pointsselected respectively from three areas obtained by dividing, into three,a first cross section perpendicular to the sputtering surface in thethickness direction (in the following Examples, three points set at 1.5mm intervals on a straight line extending in the thickness direction ofa sample having a 5 mm thickness), and three points selectedrespectively from three areas obtained by dividing, into three, a secondcross section perpendicular to the sputtering surface and the firstcross section in the thickness direction (in the following Examples,three points set at 1.5 mm intervals on a straight line extending in thethickness direction of a sample having a 5 mm thickness). Then, anenlarged picture of each measurement point is taken using an opticalmicroscope. The picture is taken at a magnification (e.g., ×50 or ×100)enabling easy measurement of the crystal grain size. Straight lines aredrawn horizontally and vertically so as to pass the center of theenlarged picture, and the number of crystal grains cut by each line iscounted. The crystal grain at the end of the line is counted as 0.5. Thelengths of the respective horizontal and vertical lines are divided bytheir corresponding number of crystal grains to determine the averagegrain size for the horizontal line and that for the vertical line. Then,the average value of the determined average grain size values for thehorizontal and vertical lines is defined as the average grain size ofone sample.

In this manner, an average value (AD_(av1)) of the crystal grain size inthe sputtering surface, an average value (AD_(av2)) of the crystal grainsize in the first cross section, and an average value (AD_(av3)) of thecrystal grain size in the second cross section are determined. Theaverage values (AD_(av1), AD_(av2), and AD_(av3)) of the crystal grainsize in the sputtering surface, first cross section, and second crosssection are further averaged, and the obtained average value is definedas an average value (AD_(tav)) of the crystal grain size (the averagecrystal grain size) of the entire plate-shaped Au sputtering target.

In the plate-shaped Au sputtering target, the ratio (AD_(av1)/AD_(tav))of the average crystal grain size (AD_(av1)) in the sputtering surfaceto the average crystal grain size (AD_(tav)) of the entire target, theratio (AD_(av2)/AD_(tav)) of the average crystal grain size (AD_(av2))in the first cross section to the average crystal grain size (AD_(tav))of the entire target, and the ratio (AD_(av3)/AD_(tav)) of the averagecrystal grain size (AD_(av3)) in the second cross section to the averagecrystal grain size (AD_(tav)) of the entire target each preferably fallwithin the range of 0.8 to 1.2. That is, a variation in the averagecrystal grain size of the Au sputtering target is preferably within±20%. By thus reducing the location-dependent variation in the averagecrystal grain size of the Au sputtering target, the flying direction ofparticles during sputtering is made uniform, which improves theuniformity of the film thickness distribution.

In the case of the cylindrical Au sputtering target, the following ninemeasurement points are set: three points set at 10 mm intervals on afirst straight line extending parallel to the cylindrical axis in thesputtering surface (cylindrical surface), three points set at 10 mmintervals on a second straight line obtained by rotating the firststraight line by 90°, and three points selected respectively from threeareas obtained by dividing, into three, a cross section perpendicular tothe cylindrical axis in the thickness direction (in the followingExamples, three points set at 1.5 mm intervals on a straight lineextending in the thickness direction of a sample having a 5 mmthickness). An average value (AD_(av1)) of the crystal grain size on thefirst straight line in the sputtering surface, an average value(AD_(av2)) of the crystal grain size on the second straight line, and anaverage value (AD_(av3)) of the crystal grain size in the cross sectionare determined. The average values (AD_(av1), AD_(av2), and AD_(av3)) ofthe sputtering surface and cross section are further averaged, and theobtained average value is defined as an average value (AD_(tav)) of thecrystal grain size of the entire cylindrical Au sputtering target.

In the cylindrical Au sputtering target, the ratio (AD_(av1)/AD_(tav))of the first average crystal grain size (AD_(av1)) in the sputteringsurface to the average crystal grain size (AD_(tav)) of the entiretarget, the ratio (AD_(av2)/AD_(tav)) of the second average crystalgrain size (AD_(av2)) in the sputtering surface to the average crystalgrain size (AD_(tav)) of the entire target, and the ratio(AD_(av3)/AD_(tav)) of the average crystal grain size (AD_(av3)) in thecross section to the average crystal grain size (AD_(tav)) of the entiretarget each preferably fall within the range of 0.8 to 1.2. That is, avariation in the average crystal grain size of the Au sputtering targetis preferably within ±20%. By thus reducing the location-dependentvariation in the average crystal grain size of the cylindrical Ausputtering target, the flying direction of particles during sputteringis made uniform, which improves the uniformity of the film thicknessdistribution. The cylindrical Au sputtering target is rotated duringsputtering, whereby the entire cylindrical surface is sputtered, so thatthe reduction in the location-dependent variation in the average crystalgrain size of the sputtering surface (cylindrical surface) can improvethe uniformity of the film thickness distribution.

In the Au sputtering target according to the embodiment, the {110} planeof Au is preferably preferentially oriented to the sputtering surface.Au has a face-centered cubic lattice structure, and the {110} plane ismore easily sputtered than other crystal planes constituting theface-centered cubic lattice structure. By preferentially orienting thesputtering surface to the {110} plane, the flying direction of particlesduring sputtering is stabilized, whereby uniformity of the filmthickness distribution can be further improved. The preferentialorientation of the sputtering surface to the {110} plane refers to astate where the orientation index N of the {110} plane is larger than 1and the largest among the orientation indices N of all the crystalplanes, where the orientation index N of each crystal plane iscalculated according to the following Wilson's equation (1) based on adiffraction intensity ratio of each crystal plane of Au, which isobtained by X-ray diffraction for the sputtering surface of the Ausputtering target. The orientation index of the {110} plane of Au ispreferably 1.3 or more.

$\begin{matrix}{N = ( \frac{\frac{I/I_{({hkl})}}{\Sigma( {I/I_{({hkl})}} )}}{\frac{{JCPDS} \cdot {I/I_{({hkl})}}}{\Sigma( {{JCPD} \cdot {I/I_{({hkl})}}} )}} )} & (1)\end{matrix}$

In the above equation (1), I/I_((hkl)) is the diffraction intensityratio of an (hkl) plane in the X-ray diffraction, JCPDS·I/I_((hkl)) isthe diffraction intensity ratio of the (hkl) plane in JCPDS (JointCommittee for Powder Diffraction Standard) card, Σ(I/I_((hkl))) is thesum of the diffraction intensity ratios of all the crystal planes in theX-ray diffraction, and Σ(JCPDS·I/I_((hkl))) is the sum of thediffraction intensity ratios of all the crystal planes in JCPDS card.

The Au sputtering target according to the embodiment can significantlyimprove uniformity of the film thickness distribution of the Ausputtered film owing to a combination of the above-described Vickershardness of 40 or more and 60 or less, average crystal grain size of 15μm or more and 200 μm or less, and the sputtering surface to which the{110} plane of Au is preferentially oriented. That is, the individualeffects brought about by the above-described Vickers hardness, averagecrystal grain size, and preferentially oriented surface of Au actsynergistically, whereby flying property of particles during sputtering,uniformity of the flying property, and stability of the flying directionof the particles are improved. Thus, when the Au sputtered film is usedas, for example, an electrode of an electronic device like a quartzoscillator device for which miniaturization is being promoted, it ispossible to provide an Au film featured in that a variation in filmthickness and a variation in mass resulting from the film thicknessvariation are reduced and that uniformity of the film thickness and massdistributions is improved.

A method of producing the above-described Au sputtering target accordingto the embodiment has a step of producing a gold sputtering target whichis made of gold and inevitable impurities, and in which the averagevalue of the Vickers hardness is 40 or more and 60 or less, the averagecrystal grain size is 15 μm or more and 200 μm or less, and the {110}plane of gold is preferentially oriented to the sputtering surface. TheAu sputtering target production method preferably includes; a step ofpreparing a gold ingot having a gold purity of 99.99% or more; a firstprocessing step of processing the gold ingot to form a desiredplate-shaped or cylindrical gold billet; a second processing step ofprocessing the gold billet under pressure so as to reduce the platethickness thereof to form a desired plate-shaped or cylindrical targetmaterial; and a heat treatment step of applying heat treatment to thetarget material.

The Au sputtering target production method according to the embodimentwill be described in detail. For example, the plate-shaped Au sputteringtarget may be produced by a production method combining casting,cutting, forging, and heat treatment of an Au raw material. Further, inthe production of the plate-shaped Au sputtering target, rolling may beapplied in place of forging of an Au raw material. The cylindrical Ausputtering target may be produced by a production method combiningcasting, cutting, pipe machining, and heat treatment of an Au material.Examples of the pipe machining include extrusion like Raflo extrusion,drawing, and forging. By controlling a processing rate or a heattreatment temperature in each of the processing steps, theabove-described Vickers hardness, average crystal grain size,preferential crystal plane, and the like can be achieved.

The casting of the Au raw material is preferably carried out as follows.The Au raw material is melted in a graphite crucible or a ceramiccrucible in a vacuum atmosphere or an inert gas atmosphere;alternatively, the Au raw material is melted in a graphite crucible or aceramic crucible while spraying inert gas to a molten metal surfaceusing an atmospheric melting furnace or while covering a molten metalsurface with a carbon-based solid sealing material. Then, the resultantraw material is cast into a graphite mold or a cast iron mold. Then,defects on the outer peripheral surface of the casted Au ingot areground to be removed. The purity of the Au ingot is preferably 99.99% ormore (4N or more). The upper limit of the Au purity of the Au ingot isnot limited to a particular value and is set in accordance with a degreeof purity required for an Au sputtered film to be formed. Preferably,the upper limit is set to less than 99.999% considering a productionprocess of the Au sputtering target or hardness thereof.

Subsequently, the obtained Au ingot is processed into a gold billethaving a desired plate shape or cylindrical shape (first processingstep). When the plate-shaped Au sputtering target is to be produced,defects on the outer peripheral surface of, for example, a plate-shapedAu ingot are ground to be removed, whereby a plate-shaped gold billet isobtained. When the cylindrical Au sputtering target is to be produced,defects on the outer peripheral surface of, for example, a cylindricalshaped Au ingot are ground to be removed and is then hollowed out,whereby a cylindrical shaped gold billet is obtained.

Subsequently, the gold billet is processed into a desired plate-shapedor cylindrical target material (second processing step). When theplate-shaped Au sputtering target is to be produced, a plate-shaped Auingot is forged into a desired plate shape. The Au ingot forging ispreferably performed in a hot state at a temperature in the range of200° C. or more and 800° C. or less and at a processing rate (sectionalarea reduction or thickness reduction) of 50% or more and 90% or less.The forging may be performed plurality of times, and heat treatment maybe applied during the forging. When the forging is performed pluralityof times, the total processing rate is adjusted to 50% or more and 90%or less.

By setting the processing rate in the forging to 50% or more, a caststructure is destroyed, and thus a uniform recrystallized structure iseasily obtained. In addition, controllability and uniformity of thehardness or crystal grain size in the subsequent heat treatment processcan be enhanced. The obtained Au forged material may be subjected tocold rolling as needed. The processing rate in the rolling is preferably50% or more and 90% or less, although it depends on the processing ratein the forging process. In place of the forging process, the rollingprocess may be applied as the Au ingot processing. As in the forging,the Au ingot rolling is preferably performed in a hot state at atemperature in the range of 200° C. or more and 800° C. or less and at aprocessing rate (sectional area reduction or thickness reduction) of 50%or more and 90% or less.

When the cylindrical Au sputtering target is to be produced, a columnarAu billet is processed into a pipe shape by, for example, extrusion likeRaflo extrusion, drawing, or forging. When the Raflo extrusion isapplied, it is preferably performed in a cold state. Further, in theRaflo extrusion, the outer diameter and thickness of a pipe to be formedare controlled by the shape (inner diameter, etc.) of a die and theshape (outer diameter, etc.) of a mandrel. At this time, an extrusionratio (billet outer diameter/pipe outer diameter) is preferably adjustedto 1.5 or more and 3.0 or less. When the extrusion ratio is 1.5 or more,a cast structure is destroyed, and thus a uniform recrystallizedstructure is easily obtained. In addition, controllability anduniformity of the hardness in the subsequent heat treatment process canbe enhanced. However, when the extrusion ratio exceeds 3.0, internalstrain becomes too large, and cracks, wrinkles, and other defects aremore likely to occur.

When drawing is applied, an Au material pipe produced by the extrusionor hollowing is preferably processed into a desired pipe shape throughcold drawing. Further, in the drawing, the outer diameter and thicknessof a pipe to be formed are controlled by the shape (inner diameter,etc.) of a die and the shape (outer diameter, etc.) of a plug. At thistime, a processing rate per drawing process is preferably adjusted to 2%or more and 5% or less. The drawing is preferably performed plurality oftimes and, in such a case, the total processing rate is preferablyadjusted to 50% or more and 90% or less. When the total processing rateis 50% or more, a cast structure is destroyed, and thus a uniformrecrystallized structure is easily obtained. In addition,controllability and uniformity of the hardness in the subsequent heattreatment process can be enhanced. However, when the total processingrate exceeds 90%, internal strain becomes too large, and cracks,wrinkles, and other defects are more likely to occur.

When forging is applied, an Au material pipe produced by the extrusionor hollowing is preferably forged in a hot state at a temperature in therange of 200° C. or more and 800° C. or less into a desired pipe shape.Further, by controlling a processing rate during forging, the outerdiameter and thickness of a pipe to be formed are controlled. In theforging, the processing rate is preferably adjusted to 30% or more and80% or less. When the processing rate is 30% or more, a cast structureis destroyed, and thus a uniform recrystallized structure is easilyobtained. In addition, controllability and uniformity of the hardness inthe subsequent heat treatment process can be enhanced. However, when theprocessing rate exceeds 80%, internal strain becomes too large, andcracks, wrinkles, and other defects are more likely to occur.

Then, the plate-shaped target material produced through the forging orrolling and the pipe-shaped target material produced through the pipemachining are subjected to heat treatment at a temperature of 200° C. ormore and 500° C. or less under an air atmosphere or inert gasatmosphere, for example to recrystallize the metal structure of thetarget material. Through such heat treatment, an Au sputtering targethaving a Vickers hardness of 40 or more and 60 or less can be obtained.Further, an Au sputtering target having an average crystal grain size of15 μm or more and 200 μm or less and/or an Au sputtering target in whichthe sputtering surface is preferentially oriented to the {110} plane canbe obtained. The heat treatment may be performed plurality of times.After the heat treatment, the sputtering target may be shaped as neededby, for example, cutting.

When the heat treatment temperature is less than 200° C., internalstrain generated during processing cannot be removed sufficiently, whichmay increase the Vickers hardness to more than 60. Further, the heattreatment temperature of less than 200° C. fails to sufficientlyrecrystallize the metal structure of the target material, which may failto preferentially orient the sputtering surface to the {110} plane. Onthe other hand, when the heat treatment temperature exceeds 500° C., theVickers hardness may become less than 40. Further, a recrystallizedstructure excessively grows, which may cause the average crystal grainsize to exceed 200 μm or cause the sputtering surface to bepreferentially oriented to a crystal plane other than the {110} plane.The holding time of heat treatment temperature, i.e., heat treatmenttime is preferably 10 min or more and 120 min or less, for example. Anexcessively short heat treatment time may fail to achieve sufficientstrain removal or sufficient recrystallization of a metal structure. Onthe other hand, an excessively long heat treatment time may result in anexcessive reduction in the Vickers hardness or an excessive increase inthe average crystal grain size.

As described above, by controlling the processing rate when processingthe Au ingot into the plate shape or cylindrical shape and thetemperature in the heat treatment for recrystallization, an Ausputtering target having a Vickers hardness of 40 or more and 60 or lessand small in variation in the Vickers hardness can be obtained. Further,an Au sputtering target having an average crystal grain size of 15 μm ormore and 200 μm or less and small in variation in the average crystalgrain size, and/or an Au sputtering target in which the sputteringsurface is preferentially oriented to the {110} plane can be obtained.By forming an Au film using such an Au sputtering target, an Au filmachieving a high film thickness distribution uniformity required for anelectrode of, for example, a quartz oscillator device can be obtained.The Au sputtering target according to the embodiment can be used forforming not only an electrode film (Au film) of a quartz oscillatordevice, but also an Au film applied to various electronic components.

The following describes a gold (Au) film production method according tothe embodiment. The gold (Au) film production method according to theembodiment includes a step of preparing a gold (Au) sputtering targetwhich is made of gold and inevitable impurities, and in which theaverage value of the Vickers hardness is 40 or more and 60 or less, theaverage crystal grain size is 15 μm or more and 200 μm or less, and the{110} plane of gold is preferentially oriented to the sputtering surfaceand a step of forming an gold (Au) film on a film-forming base materialthrough sputtering of the gold sputtering target. The step of preparingan Au sputtering target includes the steps of producing the Ausputtering target according to the above-described production method,and specific conditions therefor are as described above.

The step of forming the Au film forms the Au film on a film-forming basematerial through sputtering of the Au sputtering target according to theembodiment. As described in the above Au sputtering target productionmethod, the Au sputtering target may be a plate-shaped target or acylindrical target. In the present invention, various sputtering methodsmay be applied, such as a DC sputtering method (diode, triode, orquadode sputtering), an RF sputtering method, a magnetron sputteringmethod, an ion beam sputtering method, or an ECR (Electron CyclotronResonance) sputtering method.

In the step of forming the Au film (i.e., sputtering step), the Ausputtering target according to the embodiment and a film-forming basematerial are disposed in a vacuum chamber of a sputtering apparatus. Thefilm-forming base material may include a substrate on which the Ausputtering target according to the embodiment and the Au film aredeposited, such as a quartz substrate (quartz oscillator), asemiconductor substrate, a glass substrate, or a metal substrate, and afilm such as a resin film, a metal film, or a resin-metal compositefilm. Then, the vacuum chamber is evacuated to a predetermined vacuumlevel, and a sputtering gas such as an Ar gas or nitrogen gas isintroduced into the vacuum chamber. In this state, processing accordingto a sputtering method to be applied is performed. For example, in theDC sputtering method, RF sputtering method, and magnetron sputteringmethod, a DC voltage or an RF voltage is applied between the Ausputtering target and the film-forming base material while generatingplasma in the vacuum chamber. In the ion beam sputtering method, the Ausputtering target is irradiated with ion beam. Then, sputtered particles(Au particles), which are released from the Au sputtering target bymeans of ionized sputtering gas molecules or by irradiation of the ionbeam, are deposited onto the film-forming base material, to thereby formthe Au film.

Sputtering conditions in the Au film formation step, for example, vacuumlevel, sputtering gas pressure, power to be applied between thesputtering target and the base material, and the distance between targetand the base material are not particularly limited and are appropriatelyset according to, for example, an applied sputtering method, an appliedsputtering apparatus, the shape of the Au sputtering target, and thethickness and area of an Au film to be formed. Further, a sputteringapparatus to be used in the Au film formation is also not limited to aparticular type and may be of various types, such as a single wafertype, batch type, multi-chamber type, load lock type, and in-line type.The Au sputtering target may be a plate-shaped target or a cylindricaltarget, as described above, and thus, a sputtering apparatus is selectedaccording to the shape of the Au sputtering target.

The sputtering method and conditions to be used in the Au film formationstep are not limited to those described in Examples to be describedlater. For example, the Au film may be formed under the followingconditions. That is, the Au sputtering target and film-forming basematerial are set in a DC sputtering apparatus. The sputtering apparatusis vacuum-evacuated to an ultimate vacuum of 8×10⁻⁴ Pa or less. Afterachievement of the above vacuum level, an Ar gas is introduced into thesputtering apparatus, and the film-forming base material is etched for,e.g., 5 min with the vacuum level adjusted to, e.g., about 0.4 Pa ormore and about 0.53 Pa or less. Then, after the adjustment of the vacuumlevel to, e.g., about 0.4 Pa or more and about 0.53 Pa or less,pre-sputtering is performed with applied power of DC 500 W for 5 minAfter the adjustment of the vacuum level to, e.g., about 0.4 Pa or moreand about 0.53 Pa or less, sputtering is performed with applied power ofDC 500 W for 5 min, to thereby form an Au film. The formed film iscooled in the sputtering apparatus for one hour.

According to the above-described Au film production method of theembodiment, an Au film excellent in uniformity of a film thicknessdistribution can be obtained based on the Vickers hardness and averagecrystal grain size of the Au sputtering target used for the Au filmformation and the plane ({110} plane) preferentially oriented to thesputtering surface. Thus, an Au film having high uniformity of a filmthickness distribution and having high resistance uniformity achievedbased on the high film thickness distribution uniformity can be providedfor various devices, such as quartz oscillator devices, semiconductordevices, LED devices, LCD devices, OLED devices, magnetic devices,battery devices, and optical devices, and for various materials such aselectronic materials and functional materials. As a result, an increasein production yield, a reduction in size, an increase in performance,etc. of various devices and various functional materials can beachieved.

As described above, it is important to reduce a variation in the filmthickness of the Au film during film formation and, in order to achievethis, optimization of Au film formation conditions is critical.According to the film formation method of the embodiment, a variation inthe film thickness can be reduced, thus widening selection range of thefilm formation conditions and simplifying condition setting for filmformation, which allows an efficient Au film formation. Further, a smallvariation in the film thickness of the Au film allows a variation in themass of the Au film to be reduced in, for example, a quartz oscillator,so that product yield can be improved.

EXAMPLES

The following describes specific Examples of the present invention andevaluation results thereof.

Example 1

First, an Au mass was put into a graphite crucible and melted. Anobtained Au molten was cast into a graphite mold to produce aplate-shaped Au ingot. The surface of the Au ingot was ground, wherebyan Au billet (purity: 99.99%, analyzed by solid-state emissionspectrometry and ICP) having a width of 190 mm, a length of 270 mm, anda thickness of 50 mm was produced. Subsequently, the Au billet washot-forged at a temperature of 800° C., whereby an Au target materialhaving a width of 70 mm, a length of 200 mm, and a thickness of 45 mmwas obtained. The processing rate in the forging was set to 80% for allthree-axis directions. The Au target material after forging wassubjected to heat treatment at a temperature of 500° C. for 30 minutes.The Au target material after the heat treatment was ground to produce acircular plate-shaped Au sputtering target having a diameter of 152.4 mmand a thickness of 5 mm. For measurement of characteristics of eachportion and measurement of film thickness characteristics, two Ausputtering targets were prepared. In this regard, the same applies tothe following Examples and Comparative Examples.

The Vickers hardness of the obtained Au sputtering target was measuredaccording to the above-described plate-shaped sputtering targetmeasurement method (apparatus name: mitsutoyo HM123). The Vickershardness was measured at the above-described measurement points with a200 gf test force (pressing load). The results were as follows: theaverage value (HV_(av1)) of the Vickers hardness in the sputteringsurface was 50.5, the average value (HV_(av2)) of the Vickers hardnessin the first cross section was 52.1, the average value (HV_(av3)) of theVickers hardness in the second cross section was 51.6, and the averagevalue (Vickers hardness (HV_(tav)) of the entire target) of theHV_(av1), HV_(av2), and HV_(av3) was 51.4. The ratios of the HV_(av1),HV_(av2), and HV_(av3) to the Vickers hardness (HV_(tav)) of the entiretarget were 0.98 (HV_(av1)/HV_(tav)), 1.01 (HV_(av2)/HV_(tav)), and 1.00(HV_(av3)/HV_(tav)), respectively.

Then, the average crystal grain size of the Au sputtering target wasmeasured according to the above-described plate-shaped sputtering targetmeasurement method (apparatus name: OLYMPUS DSX500). As a result, theaverage crystal grain size (AD_(tav)) of the entire target was 34.2 μm.Further, the sputtering surface of the Au sputtering target wassubjected to X-ray diffraction, and the preferentially oriented crystalplane was evaluated according to the above-described method. As aresult, preferential orientation of the {110} plane of Au to thesputtering surface was recognized. Further, the orientation index N ofthe {110} plane according to the above-described method was determined,and the result was 1.32. Such an Au sputtering target was subjected to afilm formation process to be described later, and the characteristics ofan Au film to be obtained were evaluated.

Examples 2 to 7, Comparative Examples 1 and 2

An Au billet produced in the same manner as in Example 1 was subjectedto forging in the same manner as in Example 1 at a processing rate shownin Table 1 to produce an Au target material. Then, the Au targetmaterial after forging was subjected to heat treatment under theconditions shown in Table 1. After that, the Au target material afterheat treatment was ground to produce an Au sputtering target having thesame shape as that of Example 1. The Vickers hardness, average crystalgrain size, preferentially oriented plane of the sputtering surface, andorientation index N of the {110} plane were measured and evaluated inthe same manner as in Example 1. The measurement results are shown inTable 2. Such an Au sputtering target was subjected to a film formationprocess to be described later, and the characteristics of an Au film tobe obtained were evaluated. In the Au sputtering target of ComparativeExample 1, a crystal grain boundary failed to be clearly identified, sothat the average crystal grain size could not be measured (correspondingfield in Table 1 is blank (−)).

TABLE 1 Processing rate Heat treatment condition Au purity duringforging Temperature Time [%] [%] [° C.] [min] Ex. 1 99.99 80 500 30 Ex.2 99.99 80 500 60 Ex. 3 99.99 80 500 90 Ex. 4 99.99 80 400 30 Ex. 599.99 80 300 30 Ex. 6 99.99 80 400 60 Ex. 7 99.99 80 300 60 Comp. Ex. 199.99 80 100 30 Comp. Ex. 2 99.99 80 600 30

TABLE I Average crystal grain size Preferential {110} plane Vickershardness* [μm] crystal orientation HV_(tav) HV_(av1) HV_(av2) HV_(av3)AD_(tav) plane index N Ex. 1 51.4 50.5 52.1 51.6 34.2 {110} 1.32 (0.98)(1.01) (1.00) Ex. 2 49.3 49.1 48.6 50.1 35.0 {110} 1.44 (1.00) (0.99)(1.02) Ex. 3 48.3 48.5 49.2 48.3 37.8 {110} 1.38 (1.00) (1.01) (1.02)Ex. 4 53.6 52.3 55.2 53.2 38.2 {110} 1.45 (0.98) (1.03) (0.99) Ex. 555.6 56.3 55.4 55.1 37.5 {110} 1.41 (1.01) (1.00) (0.99) Ex. 6 47.9 48.647.2 47.8 35.2 {110} 1.12 (1.02) (0.99) (1.00) Ex. 7 46.5 45.6 47.3 46.533.8 {110} 1.09 (0.98) (1.02) (1.00) Comp. 77.3 77.2 78.5 76.1 — {110}4.25 Ex. 1 (1.00) (1.02) (0.98) Comp. 34.9 35.1 33.5 36.1 630.1  {100}0.28 Ex. 2 (1.01) (0.96) (1.03) *The values in parentheses eachrepresent a ratio to HV_(tav). The symbol “—” in the field of theaverage crystal grain size indicates inability to take a measurement dueto difficulty in identification of the crystal gain boundary.

The Au sputtering targets of Examples 1 to 7 and Comparative Examples 1and 2 were set in a single wafer sputtering apparatus (apparatus name:ANELVA SPF530H). After vacuum evacuation of the apparatus to 1×10⁻³ Paor less, sputtering was performed under the following conditions: Ar gaspressure, 0.4 Pa; applied power, DC 100 W; target-substrate distance, 40mm; and sputtering time, 5 min, whereby Au films were formed on 6-inchSi substrates (wafers), respectively. The film thickness distribution ofeach of the obtained Au films was evaluated as follows. The substrate onwhich the Au film had been formed was set in an X-ray fluorescencethickness meter, and the film thickness of the Au film was measuredunder the following conditions: measurement time, 60 sec; the number ofrepetitive measurements, 10; measurement start point, substrate endportion; and measurement point interval, 5 mm. Four measurement axeswere set for the film thickness measurement: two horizontal and verticalaxes passing the center of the substrate and two horizontal and verticalaxes passing the center of the substrate rotated by 45° from theoriginal position. After the measurement, 10-point average filmthickness was determined at each measurement point. Then, the standarddeviation of the measurement values obtained at the same measurementpositions on each of the four axes was determined, and an average valueof the standard deviations of measurement values at all the measurementpoints was determined. The results are shown in Table 3 as a standarddeviation σ of the film thickness. Then, the resistance value of the Aufilm was measured by a four probe method, and a standard deviation σ ofthe resistance value was determined as in the case of the filmthickness. The results are shown in Table 3 as the standard deviation σof the resistance value.

TABLE 3 Film formation evaluation result Standard deviation σ Standarddeviation σ of film thickness of resistance value Ex. 1 8.2 5.2 Ex. 27.9 4.6 Ex. 3 8.9 5.9 Ex. 4 9.1 6.1 Ex. 5 8.6 6.9 Ex. 6 8.6 6.5 Ex. 78.9 6.1 Comp. Ex. 1 14.0 10.6 Comp. Ex. 2 20.0 15.2

Table 2 and Table 3 reveal that, in the Au sputtering targets ofExamples 1 to 7, the Vickers hardness is 40 or more and 60 or less, andthe location-dependent variation in the Vickers hardness is small.Further, the average crystal grain size is 15 μm or more and 200 μm orless, the {110} plane is preferentially oriented to the sputteringsurface, and the orientation index N of the {110} plane is largerthan 1. An Au film formed by sputtering using the Au sputtering targethaving the above Vickers hardness, average crystal grain size, andpreferentially oriented plane of the sputtering surface is excellent inuniformity of the film thickness distribution and in uniformity of theresistance value.

Examples 8 to 12

An Au billet produced in the same manner as in Example 1 was subjectedto forging in the same manner as in Example 1 at a processing rate shownin Table 4 to produce an Au target material. Then, the Au targetmaterial after forging was subjected to heat treatment under theconditions shown in Table 4. After that, the Au target material afterheat treatment was ground to produce an Au sputtering target having thesame shape as that of Example 1.

TABLE 4 Processing rate Heat treatment condition Au purity duringforging Temperature Time [%] [%] [° C.] [min] Ex. 8 99.99 80 500 20 Ex.9 99.99 80 500 30 Ex. 10 99.99 80 500 120 Ex. 11 99.99 80 400 20 Ex. 1299.99 80 300 20

The Vickers hardness of the obtained Au sputtering target was measuredin the same manner as in Example 1. Further, the average crystal grainsize of the obtained Au sputtering target was measured according to theabove-described plate-shaped sputtering target measurement method. Asthe measurement results, the average crystal grains sizes (AD_(av1),AD_(av2), AD_(av3)) in the sputtering surface, first cross section, andsecond cross section, the average value (average crystal grain size(AD_(tav)) of the entire target) of the above average crystal grainsizes, and ratios of the respective AD_(av1), AD_(av2), AD_(av3) to theAD_(tav) are shown in Table 5. Further, the sputtering surface of the Ausputtering target was subjected to X-ray diffraction, and thepreferentially oriented crystal plane was evaluated according to theabove-described method. Further, the orientation index N of the {110}plane was determined according to the above-described method. Theresults are shown in Table 5. Such an Au sputtering target was subjectedto a film formation process in the same manner as in Example 1, and thestandard deviation σ of the film thickness of an Au film to be obtainedand the standard deviation σ of the resistance value of the Au film weredetermined. The results are shown in Table 6.

TABLE 5 Average crystal Vickers grain size* Preferential {110} planehardness [μm] crystal orientation HV_(tav) AD_(tav) AD_(av1) AD_(av2)AD_(av3) plane index N Ex. 8 49.8 35.0 35.2 36.1 33.8 {110} 1.43 (1.00)(1.03) (0.96) Ex. 9 47.5 36.8 36.2 37.1 36.8 {110} 1.60 (0.99) (1.01)(1.00) Ex. 10 51.2 38.4 39.1 38.5 37.6 {110} 1.51 (1.02) (1.00) (0.98)Ex. 11 50.2 34.9 35.2 36.3 33.3 {110} 1.33 (1.01) (1.04) (0.95) Ex. 1253.2 34.9 34.6 35.9 34.1 {110} 1.42 (0.99) (1.03) (0.98) Comp. 77.3 — —— — {110} 4.25 Ex. 1 Comp. 34.9 630.1  620.0 637.9 641.3 {100} 0.28 Ex.2 (0.98) (1.01) (1.00) *The values in parentheses each represent a ratioto AD_(tav). The symbol “—” in the field of the average crystal grainsize indicates inability to take measurements due to difficulty inidentification of the crystal gain boundary.

TABLE 6 Film formation evaluation result Standard deviation σ Standarddeviation σ of film thickness of resistance value Ex. 8 8.6 5.6 Ex. 98.1 4.2 Ex. 10 8.5 4.6 Ex. 11 9.3 5.9 Ex. 12 8.2 6.1 Comp. Ex. 1 14.010.6 Comp. Ex. 2 20.0 15.2

Examples 13 to 21, Comparative Examples 3 and 4

First, an Au mass was put into a graphite crucible and melted. Anobtained Au molten was cast into a graphite mold to produce an Au ingot.The surface of the Au ingot was ground, whereby an Au billet (purity:99.99%) having a width of 200 mm, a length of 300 mm, and a thickness of45 mm was produced. Subsequently, the Au billet was hot-rolled at atemperature of 800° C., whereby an Au target material having a width of70 mm, a length of 200 mm, and a thickness of 45 mm was obtained. Theprocessing rate in the rolling was set to 80% as a thickness reduction.The Au target material after rolling was subjected to heat treatmentunder the conditions shown in Table 7. The Au target material after theheat treatment was ground to produce a circular plate-shaped Ausputtering target having a diameter of 152.4 mm and a thickness of 5 mm.

TABLE 7 Processing rate Heat treatment condition Au purity duringrolling Temperature Time [%] [%] [° C.] [min] Ex. 13 99.99 80 500 20 Ex.14 99.99 80 500 30 Ex. 15 99.99 80 500 60 Ex. 16 99.99 80 500 90 Ex. 1799.99 80 500 120 Ex. 18 99.99 80 400 20 Ex. 19 99.99 80 400 30 Ex. 2099.99 80 300 20 Ex. 21 99.99 80 300 30 Comp. Ex. 3 99.99 80 100 30 Comp.Ex. 4 99.99 80 600 30

The obtained Au sputtering target was measured to determine the averagevalue (HV_(tav)) of the Vickers hardness of the entire target and theaverage crystal grain size (AD_(tav)) of the entire target in the samemanner as in Example 1. Further, the crystal plane preferentiallyoriented to the sputtering surface of the Au sputtering target wasevaluated in the same manner as in Example 1, and orientation index N ofthe {110} plane was determined in the same manner as in Example 1. Theresults are shown in Table 8. Such an Au sputtering target was subjectedto a film formation process in the same manner as in Example 1, and thestandard deviation σ of the film thickness of an Au film to be obtainedand the standard deviation σ of the resistance value of the Au film weredetermined. The results are shown in Table 9.

TABLE 8 Average crystal Vickers grain size Preferential {110} planehardness [μm] crystal orientation HV_(tav) AD_(tav) plane index N Ex. 1342.0 102.0 {110} 1.44 Ex. 14 41.8 101.4 {110} 1.46 Ex. 15 43.1 109.9{110} 1.52 Ex. 16 42.5 105.4 {110} 1.36 Ex. 17 43.8 103.2 {110} 1.41 Ex.18 45.0 103.9 {110} 1.54 Ex. 19 44.2 105.3 {110} 1.35 Ex.20 41.0 103.1{110} 1.48 Ex.21 42.5 104.0 {110} 1.31 Comp. Ex. 3 62.8 — — — Comp. Ex.4 35.5 640.0 — —

TABLE 9 Film formation evaluation result Standard deviation σ Standarddeviation σ of film thickness of resistance value Ex. 13 6.5 4.2 Ex. 146.1 5.2 Ex. 15 5.8 6.2 Ex. 16 5.5 6.1 Ex. 17 5.1 5.2 Ex. 18 5.9 4.8 Ex.19 6.8 5.8 Ex. 20 7.1 6.2 Ex. 21 6.2 5.1 Comp. Ex. 3 20.5 13.2 Comp. Ex.4 28.6 16.5

Example 22

First, an Au mass was put into a graphite crucible and melted. Anobtained Au molten was cast into a graphite mold to produce an Au ingot.The surface of the Au ingot was ground and hollowed out with a diameterof 50 mm, whereby a cylindrical Au billet (purity: 99.99%) having anouter diameter of 100 mm, an inner diameter of 50 mm, and a length of200 mm was produced. Subsequently, the cylindrical Au billet washot-forged at a temperature of 800° C. with a core material insertedinto the hollow portion thereof, whereby a pipe shaped Au targetmaterial having an outer diameter of 80 mm, an inner diameter of 50 mm,and a length of 400 mm or more was obtained. The processing rate in theforging was set to 35% as a thickness reduction. The pipe shaped Autarget material after forging was subjected to heat treatment at atemperature of 500° C. for 30 minutes. The Au target material after heattreatment was ground to produce a cylindrical Au sputtering targethaving an outer diameter of 70 mm, an inner diameter of 65 mm, and alength of 350 mm.

The Vickers hardness of the obtained Au sputtering target was measuredaccording to the above-described cylindrical sputtering targetmeasurement method. The Vickers hardness was measured at the measurementpoints with a 200 gf test force (pressing load). The results were asfollows: the average value (HV_(av1)) of the Vickers hardness on thefirst straight line in the sputtering surface was 50.6, the averagevalue (HV_(av2)) of the Vickers hardness on the second straight line inthe sputtering surface was 50.4, the average value (HV_(av3)) of theVickers hardness in the cross section was 52.0, and the average value(Vickers hardness HV_(tav) of the entire target) of the HV_(av1),HV_(av2), and HV_(av3) was 51.0. The ratios of the HV_(av1), HV_(av2),and HV_(av3) to the Vickers hardness (HV_(tav)) of the entire targetwere 0.99 (HV_(av1)/HV_(tav)), 0.99 (HV_(av2)/HV_(tav)), and 1.02(HV_(av3)/HV_(tav)), respectively.

Then, the average crystal grain size of the Au sputtering target wasmeasured according to the above-described cylindrical sputtering targetmeasurement method. As a result, the average crystal grain size(AD_(tav)) of the entire target was 38.1 μm. Further, the sputteringsurface of the Au sputtering target was subjected to X-ray diffraction,and the preferentially oriented crystal plane was evaluated according tothe above-described method. As a result, preferential orientation of the{110} plane of Au to the sputtering surface was recognized. Then, theorientation index N of the {110} plane according to the above-describedmethod was determined, and the result was 1.31. Such a cylindrical Ausputtering target was subjected to a film formation process to bedescribed later, and the characteristics of an Au film to be obtainedwere evaluated.

Examples 23 to 28, Comparative Examples 5 and 6

An Au billet produced in the same manner as in Example 22 was subjectedto forging in the same manner as in Example 22 at a processing rateshown in Table 10 to produce an Au target material. Then, the Au targetmaterial after the forging was subjected to heat treatment under theconditions shown in Table 10. After that, the Au target material afterheat treatment was ground to produce an Au sputtering target having thesame shape as that of Example 22. The Vickers hardness and averagecrystal grain size (AD_(tav)) of the Au sputtering target were measuredin the same manner as in Example 22. Further, the crystal planepreferentially oriented to the sputtering surface of the Au sputteringtarget was evaluated in the same manner as in Example 22, andorientation index N of the {110} plane was determined in the same manneras in Example 22. The results are shown in Table 11. Such a cylindricalAu sputtering target was subjected to a film formation process to bedescribed later, and the characteristics of an Au film to be obtainedwere evaluated.

TABLE 10 Au Processing rate Heat treatment condition purity duringforging Temperature Time [%] [%] [° C.] [min] Ex. 22 99.99 35 500 30 Ex.23 99.99 35 500 60 Ex. 24 99.99 35 500 90 Ex. 25 99.99 35 400 30 Ex. 2699.99 35 300 30 Ex. 27 99.99 35 400 60 Ex. 28 99.99 35 300 60 Comp. Ex.5 99.99 35 100 30 Comp. Ex. 6 99.99 35 600 30

TABLE 11 Average crystal grain size Preferential {110} plane Vickershardness* [μm] crystal orientation HV_(tav) HV_(av1) HV_(av2) HV_(av3)AD_(tav) plane index N Ex. 22 51.0 50.6 50.4 52.0 38.1 {110} 1.31 (0.99)(0.99) (1.02) Ex. 23 51.5 50.6 51.3 52.6 41.2 {110} 1.52 (0.98) (1.00)(1.02) Ex. 24 50.4 49.2 51.2 50.7 35.1 {110} 1.52 (0.98) (1.02) (1.01)Ex. 25 53.7 53.1 54.1 54.0 38.6 {110} 1.43 (0.99) (1.01) (1.00) Ex. 2655.8 56.0 55.5 55.9 42.8 {110} 1.35 (1.00) (0.99) (1.00) Ex. 27 49.249.8 48.6 49.2 39.8 {110} 1.18 (1.01) (0.99) (1.00) Ex. 28 49.6 51.249.2 48.3 40.8 {110} 1.09 (1.03) (0.99) (0.97) Comp. 78.1 78.1 77.1 75.0— {110} 4.98 Ex. 5 (1.00) (1.00) (0.98) Comp. 35.1 36.2 33.8 35.2 509.5{100} 0.38 Ex. 6 (1.03) (0.96) (1.00) *The values in parentheses eachrepresent a ratio to HV_(tav). The symbol “—” in the field of theaverage crystal grain size indicates inability to take a measurement dueto difficulty in identification of the crystal gain boundary.

The Au sputtering targets of Examples 22 to 28 and Comparative Examples5 and 6 were set in a cylindrical sputtering apparatus. After vacuumevacuation of the apparatus to 1×10⁻³ Pa or less, sputtering wasperformed under the following conditions: Ar gas pressure, 0.4 Pa;applied power, DC 100 W; target-substrate distance, 40 mm; andsputtering time, 5 min, whereby Au films were formed on 6-inch Sisubstrates (wafers), respectively. The film thickness distribution ofeach of the obtained Au films was measured according to theabove-described method to determine the standard deviation σ of the filmthickness of an Au film to be obtained. Further, the standard deviationσ of the resistance value of the Au film was determined according to theabove-described method. The results are shown in Table 12.

TABLE 12 Film formation evaluation result Standard deviation σ Standarddeviation σ of film thickness of resistance value Ex. 22 8.1 4.6 Ex. 238.6 5.1 Ex. 24 7.5 5.9 Ex. 25 8.5 4.8 Ex. 26 9.1 4.8 Ex. 27 8.6 5.2 Ex.28 8.9 5.6 Comp. Ex. 5 20.1 16.4 Comp. Ex. 6 25.6 15.1

Table 11 and Table 12 reveal that, in the Au sputtering targets ofExamples 22 to 28, the Vickers hardness is 40 or more and 60 or less,and the location-dependent variation in the Vickers hardness is small.Further, the average crystal grain size is 15 μm or more and 200 μm orless, the {110} plane is preferentially oriented to the sputteringsurface, and the orientation index N of the {110} plane is largerthan 1. An Au film formed by sputtering using the Au sputtering targethaving the above Vickers hardness, average crystal grain size, andpreferentially oriented plane of the sputtering surface is excellent inuniformity of the film thickness distribution and in uniformity of theresistance value.

Examples 29 to 33

An Au billet produced in the same manner as in Example 22 was subjectedto forging in the same manner as in Example 22 at a processing rateshown in Table 13 to produce a cylindrical Au target material. Then, theAu target material after the forging was subjected to heat treatmentunder the conditions shown in Table 13. After that, the Au targetmaterial after heat treatment was ground to produce an Au sputteringtarget having the same shape as that of Example 22.

TABLE 13 Heat treatment Processing rate condition Au purity duringforging Temperature Time [%] [%] [° C.] [min] Ex. 29 99.99 35 500 20 Ex.30 99.99 35 500 30 Ex. 31 99.99 35 500 120 Ex. 32 99.99 35 400 20 Ex. 3399.99 35 300 20

The Vickers hardness of the obtained Au sputtering target was measuredin the same manner as in Example 22. Further, the average crystal grainsize of the obtained Au sputtering target was measured according to theabove-described cylindrical sputtering target measurement method. As themeasurement results, the average crystal grains sizes (AD_(av1),AD_(av2), AD_(av3)) in the first sputtering surface, second sputteringsurface, and cross section, the average value (average crystal grainsize (AD_(tav)) of the entire target) of the above average crystal grainsizes, and ratios of the respective AD_(av1), AD_(av2), AD_(av3) to theAD_(tav) are shown in Table 14. Further, the sputtering surface of theAu sputtering target was subjected to X-ray diffraction, and thepreferentially oriented crystal plane was evaluated according to theabove-described method. Further, the orientation index N of the {110}plane was determined. The results are shown in Table 14. Such an Ausputtering target was subjected to a film formation process in the samemanner as in Example 22, and the standard deviation σ of the filmthickness of an Au film to be obtained and the standard deviation σ ofthe resistance value of the Au film were determined. The results areshown in Table 15.

TABLE 14 Average crystal Vickers grain size* Preferential {110} planehardness [μm] crystal orientation HV_(tav) AD_(tav) AD_(av1) AD_(av2)AD_(av3) plane index N Ex. 29 52.8 103.1 101.2 102.6 105.6 {110} 1.55(0.98) (0.99) (1.02) Ex. 30 51.2 108.1 105.3 104.6 108.1 {110} 1.35(0.99) (0.99) (1.02) Ex. 31 49.3 109.8 109.2 110.2 110.1 {110} 1.42(0.99) (1.00) (1.00) Ex. 32 54.6 106.1 102.2 104.1 106.1 {110} 1.51(0.98) (1.00) (1.02) Ex. 33 55.5 103.2 103.2 105.2 101.1 {110} 1.48(1.00) (1.02) (0.98) Comp. 78.1 — — — — {110} 4.98 Ex. 5 Comp. 35.1509.5 510.2 506.2 512.0 {100} 0.38 Ex. 6 (1.00) (0.99) (1.00) *Thevalues in parentheses each represent a ratio to AD_(tav). The symbol “—”in the field of the average crystal grain size indicates inability totake measurements due to difficulty in identification of the crystalgain boundary.

TABLE 15 Film formation evaluation result Standard deviation σ Standarddeviation σ of film thickness of resistance value Ex. 29 8.6 4.1 Ex. 308.1 4.6 Ex. 31 8.5 4.0 Ex. 32 9.3 5.9 Ex. 33 8.2 5.7 Comp. Ex. 5 20.116.4 Comp. Ex. 6 25.6 15.1

What is claimed is:
 1. A gold film production method comprising:preparing a gold sputtering target which is made of gold and inevitableimpurities and in which an average value of Vickers hardness is 40 ormore and 60 or less, an average value of crystal grain size is 30 μm ormore and 200 μm or less, and a {110} plane of gold is preferentiallyoriented to a surface to be sputtered of the gold sputtering target; andforming a gold film on a film-forming base material through sputteringof the gold sputtering target, and wherein the surface to be sputteredis subjected to X-ray diffraction, and an orientation index N of eachcrystal plane is found according to the following equation (1) based ona diffraction intensity ratio of each of the crystal plane of gold, theorientation index N of the {110} plane of gold is larger than 1, and thelargest among the orientation indices N of all the crystal planes:$\begin{matrix}{N = ( \frac{\frac{I/I_{({hkl})}}{\sum( {I/I_{({hkl})}} }}{\frac{{JCPDS} \cdot {I/I_{({hkl})}}}{\sum( {{JCPDS} \cdot {I/I_{({hkl})}}} }} )} & \lbrack {{Equation}(1)} \rbrack\end{matrix}$ where I/I_((hkl)) is the diffraction intensity ratio of an(hkl) plane in the X-ray diffraction, JCPDS·I/I_((hkl)) is thediffraction intensity ratio of the (hkl) plane provided on the JCPDScard for gold, Σ(I/I_((hkl))) is the sum of the diffraction intensityratios of all the crystal planes in the X-ray diffraction, andΣ(JCPDS·I/I_((hkl))) is the sum of the diffraction intensity ratios ofall the crystal planes provided on the JCPDS card for gold.
 2. The goldfilm production method according to claim 1, wherein the average valueof the Vickers hardness in the gold sputtering target is 45 or more and55 or less, the average crystal grain size in the gold sputtering targetis 30 μm or more and 150 μm or less, and the orientation index N of the{110} plane of gold is 1.3 or more.
 3. The gold film production methodaccording to claim 1, wherein when the gold sputtering target isplate-shaped, the average value of the Vickers hardness of thesputtering target (HV_(tay)) is an average value of: an average value ofthe Vickers hardness of the surface to be sputtered (HV_(av1)); anaverage value of the Vickers hardness on a first cross-sectionorthogonal to the surface to be sputtered (HV_(av2)); and an averagevalue of the Vickers hardness on a second cross-section perpendicular tothe first cross-section (HV_(av3)), and when the gold sputtering targetis cylindrical, the average value of the Vickers hardness of the goldsputtering target (HV_(tav)) is an average value of: an average value ofthe Vickers hardness on an arbitrary first straight line parallel to acylinder axis of the surface to be sputtered (HV_(av1)); an averagevalue of the Vickers hardness on a second straight line rotated by 90°from the first straight line (HV_(av2)); and an average value of theVickers hardness of the cross section orthogonal to the cylinder axis(HV_(av3)).
 4. The gold film production method according to claim 1,wherein when the gold sputtering target is plate-shaped, the averagevalue of the average crystal grain size of the gold sputtering target(AD_(tav)) is an average value of: an average value of the averagecrystal grain size on the surface to be sputtered (AD_(av1)); an averagevalue of the average crystal grain size on a first cross-sectionorthogonal to the surface to be sputtered (AD_(av2)); and an averagevalue of the surface to be sputtered; and the average value of theaverage crystal grain size on a second cross-section at right angle tothe surface to be sputtered and the first cross-section (AD_(av3)), andwhen the gold sputtering target is cylindrical, the average value of theaverage crystal grain size of the gold sputtering target (AD_(tav)) isan average value of: the average value of the average crystal grain sizeon an arbitrary first straight line parallel to a cylinder axis on thesurface to be sputtered(AD_(av1)); the average value of the averagecrystal grain size on a second straight line rotated by 90° from thefirst straight line(AD_(av2)); and the average value of the averagecrystal grain size on a cross-section orthogonal to the cylinder axis(AD_(av3)).
 5. The gold film production method according to claim 3,wherein the gold sputtering target is plate-shaped, and the ratioHV_(av1)/HV_(tav), the ratio HV_(av2)/HV_(tav), and the ratioHV_(av3)/HV_(tav) all fall within the range of 0.8 to 1.2.
 6. The goldfilm production method according to claim 3, wherein the gold sputteringtarget is cylindrical, and the ratio HV_(av1)/HV_(tav), the ratioHV_(av2)/HV_(tav), and the ratio HV_(av3)/HV_(tav) all fall within therange of 0.8 to 1.2.
 7. The gold film production method according toclaim 4, wherein the gold sputtering target is plate-shaped, and theratio AD_(av1)/AD_(tav), the ratio AD_(av2)/AD_(tav), and the ratioAD_(av3)/AD_(tav) all fall within the range of 0.8 to 1.2.
 8. The goldfilm production method according to claim 4, wherein the gold sputteringtarget is cylindrical, and the ratio AD_(av1)/AD_(tav), the ratioAD_(av2)/AD_(tav), and the ratio AD_(av3)/AD_(tav) all fall within therange of 0.8 to 1.2.